Custom 70cc engine build

Is it worth it or stupid?

  • YES

    Votes: 20 62.5%

  • Hell no

    Votes: 2 6.3%

  • Kinda

    Votes: 4 12.5%

  • YES

    Votes: 3 9.4%

  • Nah I'll pass

    Votes: 3 9.4%
  • Total voters
    32
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Polar_Bus said:
My suggestion of removing some material from the piston skirt was a suggestion based upon the fact you might only have to remove a small amount at the 4 corners of the skirt. You won't be altering the port timing in this particular case. I have no idea to what extent you need to remove metal, all's I was trying to do is get you to think in both directions. Remember this quote with respect to "grinding" engine port work : "It's WAY easier to loose 2 hp , than gain 1 hp with a grinder".
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That's exactly what I thought when I suggested taking some from the piston skirt rather than the case.
Here is some pics of one of my cylinders, I have traced around the piston skirt with the piston tdc, if it was this cylinder then I think quite a bit could be removed without messing with port timing.
15633485757517888681965148493369.jpg15633485999035182919219007198147.jpg15633486401148364748478439524113.jpg15633487026848253564896183124284.jpg15633488847787708262871399479616.jpg
 
So me personally I'd still cut the case. But I think you'll be ok taking that off the piston. Or a combination of the two. Cut the case on the intake side as it looks like it's just going to be a little nub to remove and cut the piston on the exhaust side. If you go the piston rout cut a radius not a sharp 90* corner. Sharp corners can be stress risers and fatigue the metal.
 
Z, you commented that the piston is specifically designed to be used with the crankcases you have ? That is a HUGE amount of interference. I don't know what to say. My comment is there is NO way that piston is compatible with that crankcase configuration. I was thinking like skimming .060" off the base outer edges of the piston. Guess that's not going to work. I guess moving forward, modifying the cases like Seandonato73 suggested is a better solution.
 
One would have to weigh out the consciences if something goes wrong ,in which one will be cheaper to replace ,
the block ,or the piston!
 
Seandonato73 said:
So me personally I'd still cut the case. But I think you'll be ok taking that off the piston. Or a combination of the two. Cut the case on the intake side as it looks like it's just going to be a little nub to remove and cut the piston on the exhaust side. If you go the piston rout cut a radius not a sharp 90* corner. Sharp corners can be stress risers and fatigue the metal.
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I'll cut the case, I don't like the idea of messing with the piston for some reason.
 
If your die grinder has multi speed capability , thats a big advantage. My industrial pencil grinders have a 15,000 rpm and when a sharp carbide round cutting tool grabs soft aluminum it ends up looking like a cratered mine field . Now i have a precision Dremel (adjustable RPM) tool and its much easier to control with far less risk of a "runaway" .than my pnumatic tool.
 
Polar_Bus said:
If your die grinder has multi speed capability , thats a big advantage. My industrial pencil grinders have a 15,000 rpm and when a sharp carbide round cutting tool grabs soft aluminum it ends up looking like a cratered mine field . Now i have a precision Dremel (adjustable RPM) tool and its much easier to control with far less risk of a "runaway" .than my pnumatic tool.
Click to expand...
Yes it has 6 levels of speed
 
Ok I've used it for a about, 4-5hrs and it's pretty good. Not too heavy so I have good control over it, I normally run it at 2-3 speed setting when doing my 7075 alu crankcase and it was doing good, it does get a bit hot, probably because of the air holes are right were I like to hold it so I block it a bit and it gets a little hot. Overall, so far, it's pretty good, esp for $15, now Ive never really used any other rotary tool like a Dremel or a foredome or anything, just this. But I'm sure this probably wouldn't be suited for people like Doug, who (from the looks of it) use it almost all day and put alot of stress and use on it since he's a jewler
 
dougstar said:
I use burrs quite a bit making jewllery and what i found was the worst thing is when the burr bights real hard pull your hand away from the work area? leaves track like sand paddle tiers??? so go easy don't rush it coz you cant put material back on??
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Yeah it's already done and I've experienced that, soooo annoying and left some light tracks on the red ano so very noticeable ?? my anodizing already looks like poop. So that's why I'm seriously considering just de anodizing the case and polishing it, like this IMG_2673.JPG.jpg
Would deffo look better than f***Ed up red ? and get it re anodized later on green or red again ?
 
dougstar said:
Well come on post some pics of the hack job??
Click to expand...
Lmao. Here ya go. I may have over done it on the intake side, but transfer sides (were the rear of the piston skirt was hitting) side is enough, the least I could remove actually. 1563423518917979654482975533563.jpg
tho it might not look like it, it's as smooth as a baby's bum.......well not that I've touched one cuz I'm not a pedo ???
 
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